One of the arguments open theists give for the view that God doesn't know the future exhaustively is that several biblical passages seem to indicate God changing his mind. This is indeed how the text is worded in several places. In Genesis 18, God is about to destroy Sodom and Gomorrah, but Abraham pleads with him to spare it even if there are ten righteous people there. As it turns out, there's just one, Abraham's nephew Lot. So God still destroys it, but he spares Lot. You might get the impression from the passage that God wasn't originally going to save Lot (although the text never says that).
Several times during the wilderness wanderings, you have similar events. After the golden calf incident in Exodus 32, Moses intercedes for Israel more than once within a few chapters. Each time, the text seems to say that God changes his plan about what he intends to do with Israel. First he intends to destroy all Israel and then make a new people out of Moses as he had done with Abraham before. Then God agrees to spare Israel, but he won't be with them in the same kind of manner as he had been (with the pillar of fire and cloud). Then he eventually agrees to be with them as he had before. There are a couple more shortened accounts of similar things with the rebellions in Numbers, and other examples appear throughout the Bible.
Now there's always been a way to take these passages that's consistent with classical theism. God knew what he intended to do all along, and that never changed, but the language about God changing his mind is really not about God having one intent and then changing it. It's about God's policy during one time being one thing and then the policy during the next time being something else, and what someone does at some time in between is God's reason for having a different policy. So God's policy in Exodus 32 is that he's telling Moses a plan (one he never intends to carry out, because he knows how Moses will respond) and then by the end of Exodus 34 is telling Moses his real plan, but he frames it in language Moses can understand so that Moses can see that he's really interacting with God. Describing it in atemporal language or explaining the final result before Moses has been brought to where God wants him is counterproductive. It doesn't allow Moses to experience the succession of states that he needs to experience.
But I'm not interested here in arguing exegetically for the traditional interpretation, even though I think it's the best way to make sense of these texts, often because of signs within the texts but especially in the light of the wider scriptures. What prompted me to write about these passages is something that occurred to me as I was reading one of these kinds of passages in Numbers last week. Look at the examples of God changing his mind that open theists claim as evidence for open theism. It their interpretation is true, then God initially has some plan he wants to carry out, and Abraham, Moses, or some other righteous figure comes along to convince God that his plan is bad. It violates God's character in some of these instances, particularly in the case of God saying he'll go against his promises to Abraham and destroy Israel. That's Moses' very argument. So if the open theistic interpretation of these passages is correct, it isn't just the metaphysical status of God's nature that they're revising. It isn't just the issue of God's exhaustive foreknowledge that's at stake in this debate. If the open theistic interpretation is correct, then God has some pretty seriously immoral tendencies that these wonderful people like Abraham and Moses then come along and help God to overcome by standing up against God's evil.
I think, then, that most classical theists who complain about open theism's biblical revisionism are missing the most revisionary aspect of open theism. It's not that open theists' view of God contradicts the plain statements of scripture (although I think it does) in order to take narrative passages told from a phenomenological perspective as if they are reporting the most basic metaphysical reality in careful, philosophical language. (If we did that with another passage, we'd end up with the view that the sun goes around the earth.) It's that open theistic interpretation of the very passages most commonly used to argue for open theism make God out to be thoroughly immoral in a way that it requires human righteousness to temper God's passions. Doesn't this get the Christian gospel upside-down?